Caranddriver: More on the GT-R's real horsepower

[GMusa]

What is the GT-R’s Real Horsepower? - Column

Despite what Nissan claims, the GT-R is not making the advertised 480 horsepower.


It’s a ringer,” we said among ourselves as soon as the first Nissan GT-R’s test results were in. Despite a power-to-weight ratio that’s 30 percent worse than that of the similarly priced Corvette Z06, that first GT-R outran the Z06 to 60 mph (3.3 seconds versus 3.4 for the quickest Z06 we’ve tested) and through the quarter-mile (11.5 at 124 mph versus 11.8 at 125). Even allowing for the launch advantages of all-wheel drive, the GT-R’s performance made us suspicious. It wouldn’t be hard for Nissan engineers, we surmised, to crank up the boost and thus jack up horsepower that would result in astonishing track numbers in American car-magazine tests. The GT-R was in such demand and our allotted time with it was so short, however, that we didn’t have time to strap it onto a chassis dyno and measure the horsepower.

We soon tested two more GT-Rs, and supporting our suspicions, they were considerably slower. GT-R No. 2 was 0.6 second behind the No. 1 through the quarter, and GT-R numero tres was a disturbing 1.1 seconds slower. Again, we didn’t have enough time to dyno-test those cars, but it seemed clear that the first GT-R was likely a one-of-a-kind rocket.

We finally got the opportunity to run a GT-R on a chassis dyno in May after Tony Swan returned with the example he used for the One Lap of America competition. The only problem with that car—No. 4 in our series—was that it performed about as well as the first. There were some differences, as you can see in the chart below, but those can easily be chalked up to the fact that the cars were tested on different days at different tracks. Yes, we do perform a weather correction to account for much of the ambient-condition difference, but no correction is perfect.

A brief primer on the Mustang chassis dyno we used: Picture a pair of parallel, supersized rolling pins mounted in the floor. The car is strapped down so that the front wheels are on one roller and the rears on the other. The operator puts the car in gear and, via the tires, spins these rollers, which are attached to a device that measures the applied force. A computer that ties into the car’s diagnostic plug and reads engine rpm calculates the horsepower. This power figure is what’s known as “wheel horsepower,” and it’s less than the engine horsepower that’s listed in our specs because the drivetrain components—transmission, driveshafts, bearings, differential—all have internal friction that soaks up power. How much power is lost in the journey to the road is not accurately known, but a 15-percent loss for rear-drive cars with manual transmissions and a near 20-percent loss for four-wheel-drive cars are good estimates.

On MotorCity Speed’s Mustang dyno in Commerce Township, Michigan, GT-R No. 4 produced a peak of 415 horsepower at the wheels. Based on our 20-percent loss estimate, the engine output was 519, or 39 horsepower more than Nissan’s stated 480.

So what’s up? We called Nissan, and the company says the first four cars we tested were early-build versions that received regular engine-computer software updates, which may account for the varied results we recorded. We then wondered which engine-computer calibration was the one real-world GT-R buyers would receive.

Three weeks later, a fifth GT-R arrived. This one, allegedly, was a production version with the latest—and final—engine calibration. We took it both to the test track and MotorCity’s dyno.

This car performed nearly identically to the fourth car. It smoked the quarter-mile in 11.6 seconds at 120 mph and produced 420 wheel horsepower. We also measured the turbo boost pressure in both cars, and the curves were basically identical.

Though we didn’t get a chance to dyno-test the two slower GT-Rs, three of the five were so close in performance that we believe they accurately represent the GT-R’s capability. Clearly, Nissan is delivering more than the advertised 480 horsepower. And the most likely figure is about 520, which is yet another reason to bow to the best performance value since the Corvette Z06.

Source: http://www.caranddriver.com/features...column?cid=259

Photos & Charts: http://www.caranddriver.com/features...ew-photos.html

[big swede]

Originally Posted by RamJet502

Lame! Overstating horsepower is punishable by death.

Huh? They are understating production hp which is exactly what GM has done for years with the LS family. I would much rather have the manufacturer do that to keep insurance companies at bay and it's always better to underpromise and over deliver than the other way around.
It appears that the first car had a more aggressive tune and was a rocket. Then subsequent cars had a milder tune and didn't perform as well so Nissan went back the first tune for production. No problem here, that's how it's supposed to be done.

Nissan advertises 480 horsepower and the car puts down 420 wheel hp which is closer to 520hp when you take a 20% drivetrain loss into account which is very very low for an AWD powertrain.

[63GrandSport001]

Originally Posted by big swede

Huh? They are understating production hp which is exactly what GM has done for years with the LS family. I would much rather have the manufacturer do that to keep insurance companies at bay and it's always better to underpromise and over deliver than the other way around.
It appears that the first car had a more aggressive tune and was a rocket. Then subsequent cars had a milder tune and didn't perform as well so Nissan went back the first tune for production. No problem here, that's how it's supposed to be done.

Nissan advertises 480 horsepower and the car puts down 420 wheel hp which is closer to 520hp when you take a 20% drivetrain loss into account which is very very low for an AWD powertrain.

Whats more important the flywheel horsepower or the RWHP to the actual vehicles performance?

[ptviperz]

Originally Posted by 63GrandSport001

Whats more important the flywheel horsepower or the RWHP to the actual vehicles performance?

RWHP is always the most important

Flywheel is for bench racing.

[63GrandSport001]

So in other words it doesnt matter even if the loss is 50% and the GTR is making 840BHP at the fly wheels as its only making 420 to the rear wheels and thats what its going to perform like.

[big swede]

Originally Posted by ptviperz

What goes to the wheels is always the most important

Absolutely! It doesn't really matter what the power is at the engine if you have a power robbing drivetrain. I have seen a stock 5.7 Hemi in a 300C and a Ram make a 60hp difference when it got to the wheels even though they were rated the same at the engine. The truck just has a heavier less efficient drivetrain that absorbs a lot of power.

Originally Posted by 63GrandSport001

So in other words it doesnt matter even if the loss is 50% and the GTR is making 840BHP at the fly wheels as its only making 420 to the rear wheels and thats what its going to perform like.

You got it.

[jkennedy293]

Originally Posted by 63GrandSport001

Whats more important the flywheel horsepower or the RWHP to the actual vehicles performance?

RWHP, because that is the power that is reaching the ground. You can have a huge flywheel number, but if your suspension is crap, most of the power will literally go up in smoke.

[big swede]

Originally Posted by jkennedy293

RWHP, because that is the power that is reaching the ground. You can have a huge flywheel number, but if your suspension is crap, most of the power will literally go up in smoke.

WHP since it could be RWD, FWD or AWD. Suspension will not take away hp but it can help or hurt making the tires stick which isn't really an issue on a dyno unless you have 1000+hp. The drivetrain loss comes from driveline weight and other mechanical inefficiencies in the drivetrain itself.

[Ambalanche]

I thought all manufacturers were publishing ASE certified HP numbers now. Guess not... Either way, no one can deny this is a fantastic car. The styling isn't for everyone, but it looks better in person. I wonder why Nissan would cover up the real HP numbers? It's not like they are marketing it as an econobox.

[JT87]

Loss for a conventional automatic is ~20%. Loss for a conventional manual or a DCT/DSG/AMT transmission is around 10-15%, which would put it right around 480hp.

[redTT]

So what happened to those cars with a 12+sec time? More recent examples are on average low 12 to high 11 and not the mid 11 that we were previously seeing.

[eurohazard]

Originally Posted by JT87

Loss for a conventional automatic is ~20%. Loss for a conventional manual or a DCT/DSG/AMT transmission is around 10-15%, which would put it right around 480hp.

Car and Driver got 420 wheel HP out of a production car. Assuming 20% loss....the flywheel horsepower is still substantially more than 480 hp rating. By my calculations it's ~526 hp at the flywheel. 526 x .20 (or 20%) is 105.4 HP lost. 526 - 105.4 hp = 420.8 HP at the wheels.

Originally Posted by redTT

So what happened to those cars with a 12+sec time? More recent examples are on average low 12 to high 11 and not the mid 11 that we were previously seeing.

11.6 sec and 120 mph trap speed isn't fast enough?

[JT87]

Originally Posted by eurohazard

Car and Driver got 420 wheel HP out of a production car. Assuming 20% loss....the flywheel horsepower is still substantially more than 480 hp rating. By my calculations it's ~526 hp at the flywheel. 526 x .20 (or 20%) is 105.4 HP lost. 526 - 105.4 hp = 420.8 HP at the wheels.

This is on a Mustang Dyno:

Unless the 911 Turbo is severely underrated as well, then it is just fluff (the Turbo actually advertises 7 less crank horsepower). They make essentially the same numbers. They claim essentially the same numbers.

And for comparison, a Z06:

As seen with the Z06, powertrain loss in a conventional manual is ~10-12%. Having another prop running to the front of the car (a la GTR/911) doesn't double the inefficiency from 10% to 20% (the GT-R has two shafts, since the transaxle is in the back while the motor is in the front; the 911 only has one shaft going to the front).

It doesn't have the power everyone says it does. Traction plays a huge role in 0-30 and 60ft times, but power makes trap speeds. According to R&T, they all hit the quarter mile within a tenth of each other, but the Z06 does it 7mph faster and the 911 does it 5mph faster than the GTR. Likewise, the GT-R is a second slower to 120mph than the Porsche and 2 slower than the Z06 (but if it makes more power at the wheels, has better aero, faster shifts, and better traction, should it not be faster everywhere in a straight line as well?)


That said, the suspension geometry, active suspension and computer controlling power on that GT-R is incredible.

[eurohazard]

Wow, by bringing up other cars, you're not proving your point, but adding to the confusion. And I don't mean that in a bad way.....it sounds harsher than what I'm trying to say. It's great discussion material no doubt.

All I am doing is showing the math. If the GT-R makes 420 hp on a dyno, then the flywheel HP is 526 hp based on 20% drivetrain loss. If the loss is just 12%, which is possible, but seems a bit unlikely to me seeing how it does have 2 drive shafts, AWD, DSG etc.......then 480 flywheel horsepower = 422.4 wheel hp. And that's very close to what you're saying.

[ptviperz]

Originally Posted by JT87

It doesn't have the power everyone says it does. Traction plays a huge role in 0-30 and 60ft times, but power makes trap speeds. According to R&T, they all hit the quarter mile within a tenth of each other, but the Z06 does it 7mph faster and the 911 does it 5mph faster than the GTR. Likewise, the GT-R is a second slower to 120mph than the Porsche and 2 slower than the Z06 (but if it makes more power at the wheels, has better aero, faster shifts, and better traction, should it not be faster everywhere in a straight line as well?)

No, the way I've always understood it, AWD eats your top end alive. AWD is awesome on launches, etc. I've had many AWD cars jump out on me only to pass them right back up once we were over 70-80 MPH....I think AWD drivetrain loss is pretty high, much higher than RWD. (*Note* I'm not talking about racing anyone with my Max or G, this was back in the day with my TA or Z28)

That said, I'd take any of the 3 cars listed above. I'm a big GTR fan.